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"""Bases class for interfaces to provide 'light' interface handling.
TODO:
_ implements a check method which check that an object implements the
interface
_ Attribute objects
This module requires at least python 2.2
:copyright: 2000-2010 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses
"""
__docformat__ = "restructuredtext en"
from types import ListType, TupleType
class Interface(object):
"""Base class for interfaces."""
def is_implemented_by(cls, instance):
return implements(instance, cls)
is_implemented_by = classmethod(is_implemented_by)
def implements(obj, interface):
"""Return true if the give object (maybe an instance or class) implements
the interface.
"""
kimplements = getattr(obj, '__implements__', ())
if not isinstance(kimplements, (list, tuple)):
kimplements = (kimplements,)
for implementedinterface in kimplements:
if issubclass(implementedinterface, interface):
return True
return False
def extend(klass, interface, _recurs=False):
"""Add interface to klass'__implements__ if not already implemented in.
If klass is subclassed, ensure subclasses __implements__ it as well.
NOTE: klass should be e new class.
"""
if not implements(klass, interface):
try:
kimplements = klass.__implements__
kimplementsklass = type(kimplements)
kimplements = list(kimplements)
except AttributeError:
kimplementsklass = tuple
kimplements = []
kimplements.append(interface)
klass.__implements__ = kimplementsklass(kimplements)
for subklass in klass.__subclasses__():
extend(subklass, interface, _recurs=True)
elif _recurs:
for subklass in klass.__subclasses__():
extend(subklass, interface, _recurs=True)
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